Bank filtration in the sandy littoral zone of Lake Tegel (Berlin): Structure and dynamics of the biological active filter zone and clogging processes

Abstract

a b s t r a c tThis study focused on clogging processes and on the benthic microalgal and meiofaunal assemblage in the sandy littoral zone of Lake Tegel, which are significantly involved in bank filtration, in a long-term. Our approach combined field studies and ''in situ'' experiments to highlight the structure of the biological active filter zone as well as the mechanisms and effects of clogging in the interstices that influence the infiltration process.Campaigns to measure ''in situ'' infiltration rates and hydraulic potential were conducted monthly from March 2004 to April 2005. Meiofaunal abundances and fine particulate organic matter (FPOM) were determined every 6 weeks in freeze cores down to depths of 50 cm. In parallel, concentrations of carbon, nitrogen and chlorophyll a were measured in samples of unfrozen sediment cores, that were divided in 1-cm steps down to depths of Z 10 cm. Similar sediment profiles were generated for analysis of colloidal carbohydrates, extracellular polymeric substances (EPS) and proteins between December 2005 and June 2006. Electron microscopy was used to visualize biofilm structure. Long-term experiments with natural FPOM and melamine resin particles as fluorescent tracers were performed to study ''in situ'' particle retention and transport, respectively. Additionally seston input was quantified during a 1-week period in April 2005.Infiltration rates showed a high temporal and spatial variability, but were not correlated with hydraulic conductivities as hydraulic gradients changed a lot. Likewise a correlation between infiltration rates and hydraulic potentials was not observed, indicating clogging processes. These are triggered to a high extend by biological compounds. In addition, seston input and intermittent gas intrusion are considered to reduce the hydraulic conductivity considerably. No significant ''in situ'' transport of inert natural fluorescent tracers was observed. However, a complete and permanent clogging of the sandy sediment does not occur, and daily infiltration rates of 0.7-27 L m À 2 h À 1 (mean 9 L m À 2 h À 1 ) guarantee a sufficient water supply by bank filtration for decades.

Impacts of Accumulated Particulate Organic Matter on Oxygen Consumption and Organic Micro-Pollutant Elimination in Bank Filtration and Soil Aquifer Treatment

“…For example, Hoffmann and Gunkel [14] analyzed sediment cores of Lake Tegel and reported that 17-21% of the total sediment volume was filled with suspended or attached particulate organic matter.…”

Effects of water warming on bank filtration: experimental enclosure studies

“…Long-term temperature monitoring studies are mainly performed in the centre of a lake [8], water of littoral zones under calm conditions are liable to stronger heating and cooling with an up-or downwelling of water. Particularly, shallow areas are highly relevant for bank filtration, because sediments are disaggregated by waves and meiofauna activities [9]. In contrast, deeper parts of a lake are often characterized as muddy with deposited organic material, which is slowly degradable under oxygen depression.…”

A potential phosphorous fertilizer for organic farming: recovery of phosphorous resources in the course of bioenergy production through anaerobic digestion of aquatic macrophytes

“…Since 1985, the P concentration caused by the inflow of Nordgraben and Tegeler Fließ has been reduced by an industrial-scale plant (German abbreviation: OWA) [44]. Nowadays, the nutrient status of the water bodies is mesotrophic [45], but the phosphorus content in sediment is still high (sediment samples from 2015 showed phosphorus contents between 0.647 and 1.280 kg P/Mg DM). Similarly, the additionally analyzed aquatic macrophytes Myriophyllum sp.…”